General Guidelines For Specimen Collection
Per CDC Interim Guidelines for Collection of Clinical Specimens:
Proper collection of specimens is the most important step in the laboratory diagnosis of infectious diseases. A specimen that is not collected correctly may lead to false negative test results. For detailed instruction on proper collection, click here to visit the CDC Specimen Collection Guide.
Nasopharyngeal (nasal) specimen collection /Oropharyngeal (throat) specimen collection
Use only synthetic fiber swabs with plastic or wire shafts. Do not use calcium alginate swabs or swabs with wooden shafts, as they may contain substances that inactivate some viruses and may inhibit molecular tests. CDC is now recommending collecting only the NP specimen, although OP specimen remain an acceptable specimen type. If both NP and OP specimens are collected, they should be combined in a single tube to maximize test sensitivity and limit use of testing resources.
Instructions for collecting an NP specimen: Tilt patient’s head back 70 degrees. Gently and slowly insert swab with a flexible shaft (wire or plastic) through the nostril parallel to the palate (not upwards) until resistance is encountered or the distance is equivalent to that from the ear to the nostril of the patient, indicating contact with the nasopharynx. Swab should reach depth equal to distance from nostrils to outer opening of the ear. Gently rub and roll the swab. Leave swab in place for several seconds to absorb secretions. Slowly remove swab while rotating it. Specimens can be collected from both sides using the same swab, but it is not necessary to collect specimens from both sides if the swab is saturated with fluid from the first collection. If a deviated septum or blockage create difficulty in obtaining the specimen from one nostril, use the same swab to obtain the specimen from the other nostril.
OP specimen: Insert swab into the posterior pharynx and tonsillar areas. Rub swab over both tonsillar pillars and posterior oropharynx and avoid touching the tongue, teeth, and gums.
All testing for SARS-CoV-2 should be conducted in consultation with a healthcare provider. Specimens should be collected as soon as possible once a decision has been made to pursue testing, regardless of the time of symptom onset. The guidance below addresses options for collection of specimens.
For initial diagnostic testing for SARS-CoV-2, CDC recommends collecting and testing an upper respiratory specimen. If applicable, please contact the testing laboratory to confirm accepted specimen types. Please note that nasopharyngeal and oropharyngeal specimens are not appropriate for self-collection. The following are acceptable specimens depending on the authorized SARS-CoV-2 viral test used:
- A nasopharyngeal (NP) specimen collected by trained healthcare personnel; or
- An oropharyngeal (OP) specimen collected by trained healthcare personnel; or
- A saliva specimen collected by the person being tested, either at home or at a testing site under supervision.
Swabs should be placed immediately into a sterile transport tube containing 2-3mL of viral transport medium (VTM).
The specimen and the non-bacteriostatic saline used to collect the specimen should be placed immediately into a sterile transport tube.